A relatively new concept of Municipal Solid Waste treatment is known as
bioreactor landfill technology. Bioreactor landfills are sanitary landfills that use
microbiological processes purposefully to transform and stabilize the
biodegradable organic waste constituents in a shorter period of time. One of the
most popular types of bioreactor landfills is the landfill with leachate recirculation.
However, it is observed that ammonia rapidly accumulates in landfills that
recirculate leachate and may be the component that limits the potential to
discharge excess leachate to the environment. In the facultative landfill, leachate
is nitrified biologically using an on-site treatment plant and converted by
denitrifying bacteria to nitrogen gas, a harmless end-product. In this research,
three pilot-plant scale lysimeters are used in a comparative evaluation of the
effect of recirculating treated and untreated leachate on waste stabilization rates.
The three lysimeters are filled with waste prepared with identical composition.
One is being operated as a facultative bioreactor landfill with external leachate
pre-treatment prior to recirculation, the second is being operated as an anaerobic
bioreactor landfill with straight raw leachate recirculation, and the third one is the
control unit and operated as a conventional landfill.
Apart from environmental restrictions, geotechnical constraints are also
imposed on new sanitary landfills. The scarcity of new potential disposal areas
imposes higher and higher landfills, in order to utilize the maximum capacity ofthose areas. In this context, the knowledge of the compressibility of waste
landfills represents a powerful tool to search for alternatives for optimization of
disposal areas and new solid waste disposal technologies.
This dissertation deals with and discusses the environmental and
geotechnical aspects of municipal solid waste landfills. In the Environmental
Engineering area, it compares the quality of the leachate and gas generated in
the three lysimeters and discusses the transfer of the technology studied through
lysimeters to procedures for full-scale operation.
In the geotechnical area, this dissertation discusses the compressibility
properties of the waste and provides a state-of-the-art review of MSW
compressibility studies. It also evaluates the compressibility of MSW landfills for
immediate and long-term settlements and proposes a new model for
compressibility of waste landfills.

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